JP2011010540A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply capable of easily outputting a low voltage by carrying out direct DC-AC conversion from a DC power supply, such as, storage battery to AC voltage, securing a current path for an inductor so as to improve security and decreasing the number of switches on the current path so as to improve the efficiency.SOLUTION: The power supply outputs a single-phase AC voltage Vrs by switching a step-up mode, and a step-down mode in which a single-phase AC voltage Vrs is output by alternately controlling two states: a positive connection state in which a positive voltage is output between terminals R1 and S1 with bidirectional switches 1, 2 (10, 11 in Fig.1) turned on; and a negative connection state in which a negative voltage is output between the terminals R1 and S1 with bidirectional switches 3, 4 (12, 13 in Fig.1) turned on, and a voltage is output, in such a manner, that the absolute voltage value |Vrs| of the single-phase AC voltage Vrs becomes lower than the voltage of a storage voltage 6 by controlling the time ratio of the two states.

Description

The present invention relates to a power supply device that converts direct current to single-phase alternating current.

Conventional power supply devices are equipped with inductors at the input and output and can be stepped up and down in both directions to convert power from DC power sources such as lead / lithium ions, storage batteries such as Ni-HM and electric double layer capacitors into single-phase AC A simple matrix converter was used (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2005-333783 (page 4-9, FIG. 6)

However, in the above power supply device, the switch side of the reactor L1 connected in series with one end of the battery in the step-down operation state is opened, and a current path flowing through the reactor L1 cannot be secured, so a surge voltage is generated in the reactor L1. The switch may be destroyed.
The present invention has been made in view of such problems, and directly converts a power source form and a voltage level from a DC voltage such as a storage battery to an AC voltage, and secures a current path of the inductor to improve safety. An object of the present invention is to provide a power supply apparatus that can improve power conversion efficiency by reducing the number of switches in the current path, and can easily output a low voltage from the voltage of a DC power supply.

In order to solve the above problem, according to one aspect of the present invention, the following power supply device is applied.
The power supply device is a power supply device that converts a DC power supply into a single-phase AC voltage and outputs the same, and connects one end of the first bidirectional switch and one end of the third bidirectional switch to provide a second bidirectional power supply. One end of the switch is connected to one end of the fourth bidirectional switch, the other end of the first bidirectional switch is connected to the other end of the second bidirectional switch, and the other end of the third bidirectional switch And two other one-way switches having a semiconductor switching element connected to one end of the fourth bidirectional switch and the negative electrode side of the DC power source. A first to fourth bidirectional switch; an inductor having one end connected to the positive side of the DC power supply and the other end connected to one end of the first bidirectional switch; the other end of the first bidirectional switch; 4 and a capacitor connected to the other end of the bidirectional switch. An input voltage detection unit that detects a DC power supply voltage and outputs a DC power supply voltage detection signal, an output voltage detection unit that detects a single-phase AC voltage and outputs an output voltage detection signal, and an output voltage command signal An on / off signal for driving the first to fourth bidirectional switches by inputting a DC power supply voltage detection signal and an output voltage detection signal, performing PWM control calculation so that the output voltage command signal and the output voltage detection signal match. A PWM controller that outputs a voltage when the absolute value of the output voltage command signal is greater than the DC power supply voltage detection signal, and the absolute value of the output voltage command signal is detected by the DC power supply voltage. When the signal is equal to or lower than the signal, an on / off signal for performing a step-down operation is output.

Moreover, according to the other viewpoint of this invention, the following power supply devices are applied.
The power supply device is a power supply device that converts a DC power supply into a single-phase AC voltage and outputs the same, and connects a current outflow end of the first unidirectional switch and a current inflow end of the third unidirectional switch, The current outflow end of the two unidirectional switches is connected to the current inflow end of the fourth unidirectional switch, and the current inflow end of the first unidirectional switch is connected to the current inflow end of the second unidirectional switch. The third unidirectional switch is connected to the current outflow end of the fourth unidirectional switch, and the current outflow end of the fourth unidirectional switch is connected to the negative electrode side of the DC power supply. 1 to 4 unidirectional switches, an inductor having one end connected to the positive side of the DC power source and the other end connected to the current inflow end of the first unidirectional switch, and the current outflow end of the first unidirectional switch And the current flow inflow end of the second unidirectional switch A capacitor and an output filter; an input voltage detector that detects a DC power supply voltage and outputs a DC power supply voltage detection signal; an output voltage detector that detects a single-phase AC voltage and outputs an output voltage detection signal; The voltage command signal, the DC power supply voltage detection signal, and the output voltage detection signal are input, PWM control calculation is performed so that the output voltage command signal and the output voltage detection signal match, and the first to fourth one-way switches A PWM control unit that outputs an on / off signal for driving the output voltage command signal when the absolute value of the output voltage command signal is larger than the DC power supply voltage detection signal, and the absolute value of the output voltage command signal When is less than or equal to the DC power supply voltage detection signal, an on / off signal for performing a step-down operation is output.

According to the present invention, it is possible to directly convert the power source form and voltage magnitude from a DC voltage such as a storage battery to an AC voltage, to secure the current path of the inductor, to improve safety, and to reduce the number of switches in the current path. Can improve the power conversion efficiency and easily output a low voltage.

1 is an overall configuration diagram of a power supply device according to a first embodiment of the present invention. Detailed configuration diagram of PWM control circuit 1 Diagram showing the positive connection state of the switching state in step-down mode The figure which shows the negative connection state of the switching state in step-down mode The figure which shows the current waveform which flows into the inductor L in case the average voltage (voltage value between terminal RSs) of the output voltage Vrs is 0, and the voltage waveform between terminals R1-S1 The figure which shows the current waveform which flows into the inductor L in case the average voltage (voltage average value between terminal RSs) of output voltage Vrs is positive and it is below storage battery voltage Vbat, and the voltage waveform between terminals R1-S1. The figure which shows the current waveform which flows into the inductor L in case the average voltage (voltage average value between terminal RS) is more than the storage battery voltage -Vbat, and the voltage waveform between terminals R1-S1 of the output voltage Vrs. Overall configuration diagram of a power supply device in Embodiment 2 of the present invention

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the same structure, description is abbreviate | omitted or simplified suitably by attaching | subjecting the same code | symbol.

FIG. 1 is an overall configuration diagram of a power supply device according to Embodiment 1 of the present invention. In the figure, the power supply device includes a storage battery 6, an inductor L, bidirectional switches 10 to 13, a smoothing capacitor C, an output filter 18 (for example, composed of a capacitor Co and inductors Lo1 and Lo2), an input voltage detection circuit 8, An output voltage detection circuit 9 and a PWM control circuit 1 are provided.

The bidirectional switches 10 to 13 are unidirectional switches composed of IGBTs (Srp, Spr, Snr, Sn, Srn, Ssp, Sps, Ssn, Sns) and diodes (D1 to D8), which are semiconductor switching elements. Two are connected in reverse parallel.
One end of the bidirectional switch 10 and one end of the bidirectional switch 13 are connected, one end of the bidirectional switch 12 and one end of the bidirectional switch 11 are connected, and the other end of the bidirectional switch 10 and the other of the bidirectional switch 12 are connected. The other end of the bidirectional switch 13 and the other end of the bidirectional switch 11, one end of the bidirectional switch 10 and the positive electrode side of the storage battery 6 are connected, and one end of the bidirectional switch 11 The negative electrode side of the storage battery 6 is connected.

The inductor L has one end connected to the positive electrode side of the storage battery 6 and the other end connected to one end of the bidirectional switch 10.
The capacitor C and the output filter 18 are connected to the other end of the bidirectional switch 10 and the other end of the bidirectional switch 11.

The input voltage detection circuit 8 outputs the voltage of the storage battery 6 to the PWM control circuit 1 as a storage battery voltage detection signal Vbat.
The output voltage detection circuit 9 detects a single-phase AC voltage that is an output of the power supply device, and outputs it to the PWM control circuit 1 as an output voltage detection signal Vrs.
The PWM control circuit 1 receives the output voltage command signal Voref, the DC power supply voltage detection signal Vbat, and the output voltage detection signal Vrs, and performs PWM control calculation so that the output voltage command signal Voref and the output voltage detection signal Vrs match. A gate signal (on / off signal) for driving the bidirectional switches 10 to 13 is output.

The storage battery 6 constitutes a DC power supply according to claims 1 and 2. The bidirectional switches 10 to 13 constitute first to fourth bidirectional switches, and the inductor L constitutes an inductor. Capacitor C is a smoothing capacitor. The output filter 18 includes, for example, a capacitor Co and inductors Lo1 and Lo2. The input voltage detection circuit 8 constitutes an input voltage detection unit, and the output voltage detection circuit 9 constitutes an output voltage detection unit. The PWM control circuit 1 constitutes a PWM control unit.

The PWM control circuit 1 receives the output voltage command Voref, the storage battery voltage Vbat detected by the input voltage detection circuit 8, and the output voltage detection signal Vrs detected by the output voltage detection circuit 9, and outputs the output voltage command Voref and the output voltage detection signal. PWM control calculation is performed so that Vrs matches, and a gate signal (ON / OFF signal) for switching the bidirectional switches 10 to 13 is output. Here, when the output voltage command Voref is a sine wave, a single-phase AC voltage is output.

The power supply device has a storage battery 6 and an inductor L connected in series, and is equivalent to a current source inverter (CSI) capable of power regeneration (charging the storage battery) having a boosting function. When the absolute value of the output voltage detection signal Vrs is higher than the storage battery voltage Vbat, a boosting operation is performed. During regeneration, a single-phase AC power supply is connected between the output terminals RS, and when the absolute value of the AC power supply voltage Vrs becomes higher than the storage battery voltage Vbat, a step-down operation is performed to convert the storage battery 6 from the single-phase AC power supply. Regeneration (charging) is performed.

FIG. 2 is a detailed configuration diagram of the PWM control circuit 1. In the figure, the PWM control circuit 1 includes a voltage regulator 2, a mode determiner 3, a PWM calculator 4, and a gate driver 5.

The voltage regulator 2 compares the output voltage command Voref and the output voltage detection signal Vrs detected by the output voltage detection circuit 9, and determines whether the output voltage detection signal Vrs is to be increased or decreased (stepped up or stepped down). . That is, when the output voltage detection signal Vrs is lower than the output voltage command Voref, the output voltage detection signal Vrs is increased. On the other hand, when the output voltage detection signal Vrs is higher than the output voltage command Voref, the output voltage detection signal Vrs is decreased. And outputs to the PWM calculator 4 whether to step up or step down.

The mode determiner 3 compares the absolute value | Voref | of the output voltage command Voref with the storage battery voltage Vbat detected by the input voltage detection circuit 8, and determines the operation in the step-up mode or the step-down mode. That is, when the absolute value | Voref | of the output voltage command Voref is higher than the storage battery voltage Vbat, a boosting operation (boost mode) is performed, and when the absolute value | Voref | of the output voltage command Voref is equal to or lower than the storage battery voltage Vbat, The operation is determined so that the step-down mode is performed, and the operation determination content is output to the PWM calculator 4.

The PWM calculator 4 is a PWM pulse that is a gate signal (on / off signal) for switching the bidirectional switches 10 to 13 based on the determination from the voltage regulator 2 and the operation determination content from the mode determination unit 3. Is calculated for each bidirectional switch and output to the gate driver 5. This calculation method will be described later.

The gate driver 5 uses the IGBTs (Srp, Spr, Snr, Srn, Ssp, Sps, Ssn) of the bidirectional switches 10-13 corresponding to the gate signals (ON / OFF signals) corresponding to the time of the PWM pulse calculated by the PWM calculator 4. , Sns).

First, the PWM control circuit 1 operates as follows in the boost mode.
When the potentials of the output terminals R and S are R> S,
(A1) Only Spr and Snr are turned on, the inductor L is short-circuited, and a current is passed through the inductor L.
(A2) Next, Ssn is turned on. (However, since D7 is reverse bias, it does not conduct)
(A3) Next, Snr is turned off, D7 is turned on, and Ssn is turned on, so that a current flows through the output terminal RS (open state). The current flow at this time is in the direction of R → S.
(A4) (A1) to (A3) are repeated to boost the storage battery voltage Vbat.

On the other hand, when the potentials of the terminals R and S are R <S,
(A5) Only Sps and Ssn are turned on, the inductor L is short-circuited, and a current is passed through the inductor L.
(A6) Next, Snr is turned on. (However, since D3 is reverse bias, it does not conduct)
(A7) Next, when Ssn is turned off and D3 is turned on and Snr is turned on, a current is supplied to the output terminal RS (open state). The current flow at this time is in the direction of S → R.
(A8) (A5) to (A7) are repeated to boost the storage battery voltage Vbat.

When the time of the short-circuit state of the inductor L is Ts and the time of the open state is To, the average value of the output voltage detection signal Vrs (voltage average value between the terminals RS) avr (Vrs) is calculated by the equation (1). it can.
avr (Vrs) = Vbat × (To + Ts) / To (1)

Since only a voltage higher than the storage battery voltage Vbat can be output only by such a boosting operation, even if the output voltage command Voref is a sine wave, the single-phase output voltage detection signal Vrs is not a sine wave but greatly distorted (harmonic component) including). There is no problem with a general rectification type (capacitor input type) load, but in the case of an inductive load such as a motor, the operation of the load may become unstable due to distortion (harmonic component) of the output voltage detection signal Vrs. Therefore, the step-down operation in the next step-down mode is also required.

Next, the step-down mode in the PWM control circuit 1 will be described.
FIG. 3A is a diagram illustrating a positive connection state in a switching state in the step-down mode, and FIG. 3B is a diagram illustrating a negative connection state in a switching state in the step-down mode.

In the step-down mode, the switch is operated so that the on / off state of the switch is alternately switched between a positive connection state shown in FIG. 3A and a negative connection state shown in FIG. In FIGS. 3A and 3B, the switches (Srp, Spr, Snr, Srn, Ssp, Sps, Ssn, Sns) that are IGBTs are described as mechanical switches for easy understanding.

(B1) In the positive connection state shown in FIG. 3A, Spr and Ssn are turned on, and a positive voltage is output to R1 and a negative voltage to S1.
(B2) Next, in order to perform the switching operation from the positive connection state to the negative connection state shown in FIG. 3B, first, Sps is turned on, and the inductor L is short-circuited along the path D6-Sps-D7-Ssn. . At this time, since D2 is in a reverse bias state, energization of Spr is also turned off.
(B3) Next, when Spr is turned off, Snr is turned on, and D7 is set in the reverse bias state, the energization of Ssn is also turned off.
(B4) Next, when Ssn is turned off, the negative connection state shown in FIG. 3B is established, the voltage polarity of the capacitor C is inverted, and a negative voltage is output to R1 and a positive voltage is output to S1.
(B5) Next, in order to perform the switching operation from the negative connection state shown in FIG. 3B to the positive connection state shown in FIG. 3A, first, Spr is turned on, and the inductor L is connected along the path D2-Spr-D3-Snr. Short circuit. At this time, since D6 is in the reverse bias state, the power supply to Sps is also turned off.
(B6) Next, when Sps is turned off, Ssn is turned on, and D3 is set in the reverse bias state, the Snr energization is also turned off.
(B7) Next, when Snr is turned off, the positive connection state shown in FIG. 3A is established, the voltage polarity of the capacitor C is inverted, and a positive voltage is output to R1 and a negative voltage is output to S1.
(B8) (B1) to (B7) are repeated to step down the storage battery voltage Vbat. .

The short-circuit state of the inductor L in (B2) and (B5) is an extremely short time of about several microseconds. As a result, a current path of the inductor L at the time of switching between the two states is secured, and the occurrence of a surge voltage is suppressed.

FIGS. 4 to 6 show the desired output voltage detection signal Vrs by adjusting the time of positive connection state (output time of storage battery voltage Vbat) T1 and the time of negative connection state (output time of storage battery voltage−Vbat) T2. It shows how the average voltage (the average value of the voltage between terminals RS) is obtained.
FIG. 4 shows a current waveform flowing through the inductor L and a voltage waveform between the terminals R1 and S1 when the average voltage (voltage average value between the terminals RS) of the output voltage detection signal Vrs with T1 = T2 becomes zero. FIG.
FIG. 5 shows the waveform of the current flowing through the inductor L and the terminals R1-S1 when the average voltage (voltage average between terminals RS) of the output voltage detection signal Vrs satisfying T1> T2 is positive and less than or equal to the storage battery voltage Vbat. It is a figure which shows the voltage waveform between.
FIG. 6 shows the current waveform flowing through the inductor L and the terminal R1- when the average voltage (voltage average between terminals RS) of the output voltage detection signal Vrs with T1 <T2 is negative and equal to or higher than the storage battery voltage -Vbat. It is a figure which shows the voltage waveform between S1.

The PWM control circuit 1 sets the time of the positive connection state (output time of the storage battery voltage Vbat) shown in FIG. 3A of (B1) to T1, and the time of the negative connection state (storage battery voltage −Vbat) shown in FIG. 3B of (B4). If the output time is T2, these times T1 and T2 are adjusted, and the PWM carrier frequency is sufficiently higher than the frequency of the single-phase AC voltage to be output.
The rectangular wave voltage shown in FIGS. 4 to 6 is applied between the terminals R1 and S1. The constants of the low-pass filters Lo1, Lo2, and Co, which are output filters 18, are set so that the PWM carrier frequency component is removed, and the average voltage lower than the storage battery voltage Vbat is output by adjusting the time ratio of T1 and T2. It becomes possible.

At the moment of switching from (B1) to (B4) described above (switching from the positive connection state shown in FIG. 3A to the negative connection state shown in FIG. 3B), a voltage twice as much as the storage battery voltage Vbat is applied to the inductor L. By the resonant operation of L and the capacitor C, the charge of the capacitor C is discharged and then charged to the storage battery voltage Vbat.

When T1 and T2 are equal, the voltage waveform between the terminals R1-S1 has an average voltage of the output voltage detection signal Vrs (voltage average value between the terminals R-S) substantially zero (see FIG. 4).
When T1> T2, the average voltage of the output voltage detection signal Vrs (the voltage average value between the terminals RS) is positive and equal to or less than the storage battery voltage Vbat (see FIG. 5).
On the other hand, when T1 <T2, the average voltage of the output voltage detection signal Vrs (the voltage average value between the terminals RS) is negative and equal to or higher than the storage battery voltage −Vbat (see FIG. 6).

The average current Ioff flowing through the inductor L changes in accordance with the load power Po, and is approximately expressed by an expression of Ioff≈Po / Vbat. However, this equation (Ioff≈Po / Vbat) does not include the power due to the resonance current.
Further, the average voltage value of the output voltage detection signal Vrs is given by equation (2).
Vrs = Vbat × (T1-T2) / (T1 + T2) (2)
When Vrs = Vbat, T2 = 0, and when Vrs = −Vbat, T1 = 0.
When Vrs = 0, T1 = T2.

Since T1 + T2 = Tc, where Tc is the carrier period that is the reciprocal of the carrier frequency,
In order to obtain the desired output voltage Vrs * that has been stepped down,
T1 = (Vrs * + Vbat) × Tc / (2 × Vbat) (3)
T2 = Tc−T1 (4)
Thus, T1 and T2 may be set by calculating as follows.

Thus, since Example 1 of this invention is implemented, the voltage below storage battery voltage Vbat can be output. Further, even when switching from the positive connection state shown in FIG. 3A to the negative connection state shown in FIG. 3B, the occurrence of overvoltage can be suppressed and the safety can be improved. Furthermore, since power is directly converted from the DC power source, an electrolytic capacitor for the DC bus is not required, and the number of switches on the current path is small, so that conduction loss can be reduced.

FIG. 7 is an overall configuration diagram of a power supply device according to the second embodiment of the present invention. In the figure, the power supply device includes a DC power supply 7, an inductor L, unidirectional switches 14 to 17, a capacitor C, an output filter 18 (for example, a capacitor Co and inductors Lo1 and Lo2), a PWM control circuit 1a (a PWM control circuit). 1) and a DC power supply voltage detection circuit and an output voltage detection circuit (not shown). 1 to 6 are denoted by the same reference numerals, and description thereof will be omitted or simplified as appropriate.

The one-way switches 14 to 17 are each composed of a semiconductor switching element and a diode. The one-way switch 14 and the one-way switch 16 are connected in series, and the one-way switch 17 and the one-way switch 15 are connected in series. ing. When one end of a unidirectional switch into which current flows when the unidirectional switch is turned on is defined as a current inflow end, and the other end of the unidirectional switch is defined as a current outflow end, the current outflow end of the unidirectional switch 15 and the negative electrode of the DC power source 7 are defined. Is connected to the side.

One end of the inductor L is connected to the positive side of the DC power source 7, and the other end is connected to the current inflow end of the unidirectional switch 14.
The capacitor C and the output filter 18 are connected to a connection point between the one-way switch 14 and the one-way switch 16 and a connection point between the one-way switch 17 and the one-way switch 15.

A DC power supply voltage detection circuit (not shown) detects the voltage of the DC power supply 7 and outputs a DC power supply voltage detection signal.
An output voltage detection circuit (not shown) detects a single-phase AC voltage that is an output of the power supply device and outputs an output voltage detection signal.
The PWM control circuit 1a has a function equivalent to that of the PWM control circuit 1 shown in FIG. 1, and receives the output voltage command signal Voref, the DC power supply voltage detection signal Vbat, and the output voltage detection signal Vrs, and outputs the output voltage command signal Voref. PWM control calculation is performed so that the output voltage detection signal Vrs and the output voltage detection signal Vrs coincide with each other, and a gate signal (on / off signal) for driving the one-way switches 14 to 17 is output. Although the PWM control circuit 1a is different from the PWM control circuit 1 of FIG. 1 in that the number of IGBTs to be driven is changed from eight to four, the same function is performed.

The DC power supply 7 constitutes a DC power supply according to claims 3 and 4. The unidirectional switches 14 to 17 constitute first to fourth unidirectional switches, and the inductor L constitutes an inductor. Capacitor C is a smoothing capacitor. The output filter 18 includes, for example, a capacitor Co and inductors Lo1 and Lo2. A DC power supply voltage detection circuit (not shown) constitutes an input voltage detection unit, and an output voltage detection circuit (not shown) constitutes an output voltage detection unit. The PWM control circuit 1a constitutes a PWM control unit.

In such a configuration, the power supply device can significantly reduce the number of parts. Further, the operations in the step-up mode and the step-down mode are performed in the same manner as in the first embodiment, and ON / OFF control of the one-way switches 14 to 17 is performed.

In the first and second embodiments of the present invention, a description has been given using an IGBT and a diode connected in series as a unidirectional switch element. However, a reverse conduction blocking IGBT (RB-IGBT: Reverse Blocking) is used as the unidirectional switch element. -Insulated Gate Bipolar Transistor) may be used to omit the diode. This RB-IGBT is a new device having a reverse breakdown voltage that the IGBT could not have. When this RB-IGBT is applied to a bidirectional switch, a bidirectional module can be configured without using a diode for reverse voltage protection that is essential for the IGBT.

When the storage battery 6 needs to be charged, a single-phase AC power supply is connected to the output of the power supply device, and the inductor L, the diodes D1, D4, D5, D8, and IGBT are connected with the AC potential higher than the storage battery voltage Vbat. Charging is performed by the step-down operation from the AC power source to the storage battery 6 using the switch operation of (Srp, Srn, Ssp, Sns).

On the other hand, when the charging operation to the storage battery 6 is unnecessary, or when the regenerative (charging) operation using a DC power supply is unnecessary instead of the storage battery 6, the diodes D1, D4, D5, D8 and the IGBTs (Srp, Srn, Ssp) , Sns), and a circuit in which these driving circuit and control circuit are deleted.
The power supply apparatus described in the present embodiment can be applied to a power conversion apparatus such as a portable power supply apparatus that converts a DC power supply into a single-phase AC, a system compensation apparatus (power conditioner), and an uninterruptible power supply (UPS). it can.

DESCRIPTION OF SYMBOLS 1, 1a PWM control circuit 2 Voltage regulator 3 Mode determination device 4 PWM calculator 5 Gate driver 6 Storage battery 7 DC power supply 8 Input voltage detection circuit 9 Output voltage detection circuit 10-13 Bidirectional switch 14-17 Unidirectional switch 18 Output filter Srp, Spr, Snr, Srn, Ssp, Sps, Ssn, Sns Semiconductor switching element (IGBT)
D1 to D8 Diode L, Lo1, Lo2 Inductor C, Co Capacitor

Claims (4)

A power supply device that converts a DC power supply into a single-phase AC voltage and outputs it,
One end of the first bidirectional switch and one end of the third bidirectional switch are connected, one end of the second bidirectional switch and one end of the fourth bidirectional switch are connected, and the first bidirectional switch Connecting the other end of the switch and the other end of the second bidirectional switch, connecting the other end of the third bidirectional switch and the other end of the fourth bidirectional switch, The first to fourth bidirectional switches in which two one-way switches having semiconductor switching elements connected in reverse parallel to each other and one end of the bidirectional switch connected to the negative electrode side of the DC power supply;
An inductor having one end connected to the positive side of the DC power supply and the other end connected to one end of the first bidirectional switch;
A capacitor and an output filter connected to the other end of the first bidirectional switch and the other end of the fourth bidirectional switch;
An input voltage detector that detects a voltage of the DC power supply and outputs a DC power supply voltage detection signal;
An output voltage detector that detects the single-phase AC voltage and outputs an output voltage detection signal;
An output voltage command signal, the DC power supply voltage detection signal, and the output voltage detection signal are input, and PWM control calculation is performed so that the output voltage command signal and the output voltage detection signal coincide with each other. A PWM control unit that outputs an on / off signal for driving the bidirectional switch of
The PWM control unit performs a step-up operation when the absolute value of the output voltage command signal is larger than the DC power supply voltage detection signal, and performs a step-down operation when the absolute value of the output voltage command signal is equal to or less than the DC power supply voltage detection signal. A power supply device that outputs the on / off signal. The PWM control unit outputs the on / off signal so that the boosting operation causes the inductor to be in a short circuit state or an open state,
The step-down operation outputs the on / off signal so as to adjust an output time ratio between two states of a positive connection state where the voltage across the capacitor is a positive voltage and a negative connection state where the voltage is a negative voltage. The power supply device according to claim 1. A power supply device that converts a DC power supply into a single-phase AC voltage and outputs it,
The current outflow end of the first unidirectional switch is connected to the current inflow end of the third unidirectional switch, and the current outflow end of the second unidirectional switch and the current inflow end of the fourth unidirectional switch are connected to each other. A current inflow end of the first unidirectional switch and a current inflow end of the second switch, and a current outflow end of the third unidirectional switch and a current outflow end of the fourth switch. The first to fourth unidirectional switches having a semiconductor switching element, wherein the current inflow end of the fourth unidirectional switch and the negative electrode side of the DC power source are connected,
An inductor having one end connected to the positive side of the DC power source and the other end connected to one end of the first one-way switch;
A capacitor and an output filter connected to the other end of the first unidirectional switch and the other end of the fourth unidirectional switch;
An input voltage detector that detects a voltage of the DC power supply and outputs a DC power supply voltage detection signal;
An output voltage detector that detects the single-phase AC voltage and outputs an output voltage detection signal;
An output voltage command signal, the DC power supply voltage detection signal, and the output voltage detection signal are input, and PWM control calculation is performed so that the output voltage command signal and the output voltage detection signal coincide with each other. A PWM control unit that outputs an on / off signal for driving the one-way switch of
The PWM control unit performs a step-up operation when the absolute value of the output voltage command signal is larger than the DC power supply voltage detection signal, and performs a step-down operation when the absolute value of the output voltage command signal is equal to or less than the DC power supply voltage detection signal. A power supply device that outputs the on / off signal. The PWM control unit outputs the on / off signal so that the boosting operation causes the inductor to be in a short circuit state or an open state,
The step-down operation outputs the on / off signal so as to adjust an output time ratio between two states of a positive connection state where the voltage across the capacitor is a positive voltage and a negative connection state where the voltage is a negative voltage. The power supply device according to claim 3.

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